In this work we elucidate the microscopic origin of the dominant radiation induced I-II
spectra in p-type doped 4H-SiC. By calculating the electronic g-tensor from first principles in the
framework of density functional theory, basal antisite pairs SiCCSi
+ are shown to give rise to the
characteristic anisotropic g-tensors found in the electron paramagnetic resonance (EPR)
measurements. Additional central hyperfine (hf) splittings of about 100 MHz due to the SiC antisite
nuclei are predicted theoretically and also resolved experimentally. We have, thus, identified
antisite pairs as a dominant defect in electron and proton irradiated p-type doped 4H-SiC.